Abstract:

A virtual lug loader includes a lug loader for loading workpieces in a
flow direction into the spaced apart lugs on a lugged conveyor, wherein
the workpieces are transversely oriented relative to the flow direction.
The lug loader includes an array of pairs of endless conveyors for
conveying the workpieces downstream, wherein each pair of endless
conveyors in the array include first and second endless conveyors. The
first and second endless conveyors are spaced laterally apart across the
flow direction. Each are aligned substantially in the flow direction. The
array forms a continuous upper surface in the flow direction for
supporting the workpieces translating downstream in the flow direction.
Each pair of endless conveyors in the array overlap adjacent pairs of
endless conveyors in the array. At least one pair of endless conveyors in
the array include independently actuable first and second drives
independently driving their corresponding first and second endless
conveyors.

Claims:

1. A lug loader for loading workpieces, the lug loader comprising:an array
of pairs of endless conveyors, wherein each pair of endless conveyors
includes a first and a second endless conveyor spaced laterally apart
across a flow direction and substantially aligned in said flow
direction,wherein said array forms a continuous upper surface for
supporting a workpiece translating downstream in said flow direction, the
pairs of endless conveyors overlapping in said flow direction,wherein at
least one of the pairs of endless conveyors includes independently
actuable first and second drives independently driving corresponding said
first and second endless conveyors respectively.

2. The device of claim 1 wherein said array includes an upstream gapping
section and a downstream lug loading section, wherein said at least one
of the pairs of endless conveyors is within said lug loading section.

3. The device of claim 2 wherein said pairs of endless conveyors in said
gapping section translate the workpiece in said flow direction at
increasing downstream velocities between an upstream end of said gapping
section and a downstream end of said gapping section.

4. The device of claim 3 wherein said increasing downstream velocities are
successively increasing downstream velocities corresponding to successive
said pairs of endless conveyors between said upstream and downstream ends
of said gapping section.

5. The device of claim 3 wherein substantially half of the first and
second endless conveyors in said lug loading section have corresponding
selectively actuable drives so that said each pair of endless conveyors
in said lug loading section is asymmetrically actuable to drive one
endless conveyor ahead of another endless conveyor in said each pair of
endless conveyors in said lug loading section to correct skew of a
workpiece on any one of those endless conveyors.

6. The device of claim 5 wherein said adjacent pairs of endless conveyors
in said array overlap at adjacent ends thereof by one endless conveyor of
said adjacent pairs being inset laterally across said flow direction
relative to a corresponding second endless conveyor of said adjacent
pairs.

7. A method for loading workpieces on a lugged conveyor having an array of
pairs of endless conveyors, each pair of endless conveyors including a
first and a second endless conveyor spaced laterally apart and
substantially aligned in a flow direction, wherein said array forms a
continuous upper surface in said flow direction for supporting the
workpieces translating downstream in said flow direction, and wherein at
least one pair of endless conveyors in said array includes independently
actuable first and second drives independently driving corresponding said
first and second endless conveyors respectively, the method comprising
the steps ofa) creating gaps between the workpieces by accelerating the
workpieces as they are translated downstream on the array, andb) when one
or more of the workpieces are skewed from their transverse orientation,
using said first or second drives corresponding to said at least one of
said each pair of endless conveyors to correct the skewed workpiece to an
un-skewed position oriented transversely to the flow direction.

8. The method of claim 7 wherein said array includes an upstream gapping
section and a downstream lug loading section, wherein said at least one
pair of endless conveyors is within said lug loading section.

9. The method of claim 7 wherein said pairs of endless conveyors in said
gapping section translate the workpiece in said flow direction at
increasing downstream velocities between an upstream end of said gapping
section and a downstream end of said gapping section.

10. The method of claim 8 wherein said increasing downstream velocities
are successively increasing downstream velocities corresponding to
successive said pairs of endless conveyors between said upstream and
downstream ends of said gapping section.

11. The method of claim 8 wherein substantially half of all said first and
second endless conveyors of said pairs of endless conveyors in said lug
loading section have corresponding selectively actuable drives so that
said each pair of endless conveyors in said lug loading section is
asymmetrically actuable to drive one endless conveyor ahead of another
endless conveyor in said each pair of endless conveyors in said lug
loading section to correct skew of a workpiece on any one of those
endless conveyors.

12. The method of claim 11 wherein said adjacent pairs of endless
conveyors in said array overlap at adjacent ends thereof by one endless
conveyor of said adjacent pairs being inset laterally across said flow
direction relative to a corresponding second endless conveyor of said
adjacent pairs.

[0002]This invention relates to an apparatus for the singulation or
allocation of lumber into lug spaces on a lugged transfer, or other
lumber conveying device, and in particular relates to an apparatus
capable of collecting, singulating, straightening, allocating and
consistently spacing, rough sawn lumber or planed finished lumber, or
sticks of varying widths, thickness and lengths into consecutive
spaced-apart lugs, or allocated spacings onto a transfer, or lugged
transfer, or to a stick placing device, at high speeds.

BACKGROUND OF THE INVENTION

[0003]Conventional lug loaders or singulators (hereinafter collectively
referred to as either lug loaders or singulators) have been found to be
inadequate at higher feed speeds. They are also limited in their ability
to both singulate and allocate lumber. When lumber is of varying widths
and varying in thickness, or bowed, as may be predominant in curve sawing
mills, cupped or crooked, and/or skewed on the transfer, it becomes
increasingly difficult to handle the lumber at desirable higher speeds.

[0004]An example of a conventional lug loader is that taught in U.S. Pat.
No. 3,923,142 which issued to Rysti on Dec. 2, 1975. In particular, what
is being taught is singulating boards by use of supporting arms rotating
around a closed loop, the orientation of the supporting arms controlled
by curved deflectors. Pressing arms in opposed radial pairs, are
rotatably mounted above the supporting arm to synchronously clamp a board
onto a supporting arm. Downstream flow of the mat of boards is arrested
by a stop on each supporting arm. Rysti does not disclose a mechanism for
straightening lumber which is skewed on the infeed transfer in the lug
loader.

[0005]Applicants are also aware of U.S. Pat. No. 5,518,106, which issued
to Allard on May 21, 1996. Allard discloses using fixed pick-up shoes
mounted onto rotating discs for engaging and supporting boards being
singulated. Fixed shoes however, have the disadvantage that they may mark
the underside of the board as the board is translated over the top of the
disc and as the board is released. If a board is finished, for example
destined for cabinet making or the like, then any marks from the shoe or
overhead clamp will reduce the value of the board. Allard also discloses
a speed-up belt to pull the board away from the fixed shoes at the top of
the disc to prevent the board from being flipped over as the board is
released from the shoes. In some mills the boards have been marked for
trimming and grading before the lug loader. Thus if the board has been
flipped over by the singulator, as may occur in the case of the Allard
device, the board must be flipped back by hand to read the mark. This can
be difficult in a high speed application.

[0006]Many lug loaders in the prior art, particularly those operating at
slower feed speeds, require that, in order to stop the delivery of boards
to the singulator, the board mat moving downstream into the singulator
device must be pushed back upstream by the stopping means, that is forced
away from, for example, the fixed pick-up shoe and clamping device. Worse
yet, in some prior art devices the board delivery mechanism must be
brought to a complete stop. Both pushing the mat of boards back upstream,
and stopping the board delivery mechanism, can be impractical at high
speed.

[0007]In the prior art applicant is also aware of U.S. Pat. Nos. 5,921,376
and 6,199,683 which issued to Michell et al for, respectively, a High
Speed Revolving Lug Loader With Retracting Heel and Hook and a High Speed
Revolving Board Singulator With Retracting Shoe and Variable Dwell
Duckers, both of which describe the mechanical manipulation of boards to
load the boards into individual lug spaces in a lugged outfeed transfer.

[0008]Applicant is also aware of the following U.S. Patent Nos. in the
prior art relating to the present invention: U.S. Pat. Nos. 4,077,524;
4,144,976; 4,330,055; 4,638,440; 4,869,360; 5,419,425; 5,662,203; and
5,813,512.

SUMMARY OF THE INVENTION

[0009]The proposed invention is a transfer system. The transfer system
makes use of conveyors such as chains or belts to move lumber pieces
downstream while oriented traversely across the flow path. The lumber
pieces enter the virtual lug loading system according to the present
invention moving transversely. The lumber pieces may enter as a tightly
spaced sheet or mat of pieces with no gaps, or the lumber pieces may be
randomly spaced and oriented.

[0010]Within the system a first grouping of transfers create consistent
gaps between individual lumber pieces. The speed with which the lumber
pieces are translated downstream is varied to create spaces between the
lumber pieces. The first group of transfers may be driven individually or
ganged together. In one embodiment individual transfers or pairs of
transfers are selectively and independently actuable to vary their speeds
so that the gaps may be created, for example, by increasing the velocity
of successive transfers in the downstream direction.

[0011]The transfers in the second grouping of transfers are individually
driven. They maintain the gapping, that is the spacing between lumber
pieces, and allow a surge capacity. Being individually driven, these
transfers also provide for skew correction should the lumber pieces
arrive skewed or skew during a transition from one transfer to another.
These transfers gap and straighten the pieces as required so that one
piece is positioned into each lug space on downstream lugged transfer
chains. Thus, individually driven belts within this second grouping of
transfers provide skew correction to correct the orientation of skewed
lumber pieces on the infeed to the lugged transfer being loaded. Keeping
the lumber pieces straight, that is oriented traversely across the flow
path on the infeed, helps deal the lumber pieces into the lug spaces.

[0012]Dealing the boards directly into lug spaces without a mechanical lug
loader simplifies the loading of the lug spaces in the lugged transfer as
compared to the prior art. It improves operator access, and reduces the
amount of mechanical components requiring maintenance.

[0013]In one aspect of the present invention, servo controlled decks
singulate the lumber pieces and position them directly into a lugged
chain.

[0014]In summary the virtual lug loader according to one aspect of the
present invention includes a lug loader for loading workpieces in a flow
direction into the spaced apart lugs on a lugged conveyor, wherein the
workpieces are transversely oriented relative to the flow direction. The
lug loader includes an array of pairs of endless conveyors for conveying
the workpieces downstream, wherein each pair of endless conveyors in the
array include first and second endless conveyors. The first and second
endless conveyors are spaced laterally apart across the flow direction.
Each are aligned substantially in the flow direction. The array forms a
continuous upper surface in the flow direction for supporting the
workpieces translating downstream in the flow direction. Each pair of
endless conveyors in the array overlap adjacent pairs of endless
conveyors in the array. At least one pair of endless conveyors in the
array include independently act-Liable first and second drives
independently driving their corresponding first and second endless
conveyors.

[0015]When a skewed workpiece, that is one which is skewed from its
transverse orientation, is translating on the first and second endless
conveyors, the first or second drive corresponding to one of the pair of
endless conveyors advances the upstream-most end of the workpiece
relative to its downstream-most end to correct the workpiece to an
un-skewed position oriented transversely to the flow direction.

[0016]The array may include an upstream gapping section and a downstream
lug loading section. Advantageously, the first and second endless
conveyors, that is the pair or pairs of conveyors which are independently
actuable so as to correctly orient skewed workpieces, is or are found
within the lug loading section. However, it is not intended as limiting
the scope of the present invention to have only gapping sections followed
by skew correction sections. It is intended that in the present invention
also to interleaf gapping sections with skew correction pairs. Further,
skew correction could be done anywhere within the transfer system instead
of just the lug loading section.

[0017]The pairs of endless conveyors in the gapping section may translate
the workpieces in the flow direction at increasing downstream velocities
between an upstream end of the gapping section and a downstream end of
the gapping section. The increasing downstream velocities may be
successively increasing downstream velocities corresponding to successive
pairs of endless conveyors between the upstream and downstream ends of
the gapping section.

[0018]The number or proportion of endless conveyors either overall to the
system, or within the lug loading section, which are the independently
actuable pairs of endless conveyors may be for example, not intended to
be limiting, substantially half of the number of pairs of endless
conveyors.

[0019]The independently actuable pairs of endless conveyors each have
corresponding selectively actuable drives so that each of those pairs of
endless conveyors is asymmetrically actuable to drive one endless
conveyor ahead of another endless conveyor to correct skew of a workpiece
on any one of those endless conveyors.

[0020]The adjacent pairs of endless conveyors in the array may overlap at
adjacent ends thereof by one endless conveyor of the adjacent pairs being
inset laterally across the flow direction relative to a corresponding
second endless conveyor of the adjacent pairs.

[0021]The present invention also is intended to include within its ambit a
method of virtual lug loading corresponding substantially to the use of
the above described apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 is a side elevation view of the virtual lug loader according
to the present invention shown in an elongated view having component
views in FIGS. 1A, 1B and 1C intended to be viewed side-by-side in
sequence.

[0023]FIG. 2 is a plan view of the virtual lug loader of FIG. 1 shown in
an elongated view having component views in FIGS. 2A, 2B and 2C intended
to be viewed side-by-side in sequence.

[0025]As seen in the accompanying figures wherein similar characters of
reference denote corresponding parts in each view, the Virtual Lug Loader
according to the present invention includes a gapping section 10
immediately upstream, relative to a direction of flow A, of lug loading
section 12. Workpieces 14 arrive in direction A so as to form a mat or
blanket 16 of workpieces 14 on infeed transfer 18. Workpieces 14 arriving
at the upstream end of infeed transfer 18 may be fed from, for example, a
tilt hoist, a landing table, an unscrambler, or other wood handling
machinery.

[0026]Mat 16 is formed on infeed transfer 18 as the workpieces are slowed
on transfer 5 belts At the downstream end of infeed transfer 18,
workpieces 14 are urged onto the upstream ends 22a of a first pair of
belts 22 for progressively faster translation of each workpiece 14 in
direction A as the workpieces are transferred from the downstream end of
infeed transfer 18 onto sequentially and progressively faster successive
pairs of belts 22, 24, 26, 28, and 30 within gapping section 10. Gapping
section 10 may, alternatively, may be thought of as a lumber separation
zone. Thus, a workpiece 14 having a velocity Vo in direction A on infeed
transfer 18, will, once handed off to the first pair of belts 22, have a
downstream velocity V1, and then sequentially increasing velocities V2,
V3, V4, V5 thereby sequentially increasing the separation between
individual work pieces 14 by reason of the progressive acceleration of
the boards between pairs of belts.

[0027]Advantageously, the separation between individual workpieces 14 is
increased as the length of the gaps, distance g between adjacent
workpieces is increased for example to approximately one hundred
twenty-five percent of the length of each lug space, distance l, between
lugs 32a of lugged outfeed chains 32. It is understood that, although
five pairs of belts 22-30 are illustrated, it is not intended to limit
the present invention to five pairs of belts in gapping section 10 as
more or fewer pairs of belts will suffice so long as sequential
workpieces 14 are separated in direction A so that gap distance g is at
least equal to lug space distance l.

[0028]The pairs of belts 22, 24, 26, 28 and 30 in gapping section 10 may
each be driven by variable frequency drives or induction motors 34 along
with associated gear heads. In the illustrated example, not intended to
be limiting, each of the five speed-up zones corresponding to the five
belt pairs are approximately sixteen inches long so that the length in
the downstream direction of gapping section 10 is approximately six foot,
eight inches.

[0029]In a preferred embodiment, lug loading section 12 is immediately
downstream, and cooperates with, the downstream end of gapping section 10
so that workpieces 14 are smoothly handed off from belts 30, being the
downstream most pair of belts in gapping section 10, to the first pair of
control zone belts 36 located immediately downstream of the interface B
between gapping section 10 and lug loading section 12. Lug loading
section 12 is a workpiece control zone wherein skew may be corrected such
as the skew of a workpiece 14' illustrated in dotted outline on control
zone belts 38. Skew correction is accomplished by each belt in each pair
of control zone belts 36, 38, 40, 42, 44, and 46 being able and adapted
to selectively operate at different speeds. In order to correct skew, for
example a skew angle alpha (a) of a skewed workpiece 14 the two belts 38,
and subsequent downstream belts as need be, are driven at different
speeds relative to one another as board 14' passes over the belts, so
that the lagging end of the boar catches up with the advanced end of the
board until the board is correctly positioned perpendicularly across the
direction of flow A.

[0030]Apart from operating to correct the skew of workpieces translating
downstream in direction A, the independently actuable control zone belts
in the belt pairs of lug loading section 12 also, in addition to those
belts in gapping section 10, operate to selectively space the boards
apart and synchronize the boards with upcoming lugs 32a as the lugged
outfeed chains 32 rotate in direction C. Thus the control zone belts are
driven by a motion controller (not shown) to accelerate or decelerate
pairs of belts 36, 48, 40, 42, 44 and 46 to simultaneously accelerate or
decelerate both belts in individual pairs of belts so as to accelerate or
decelerate a workpiece which has been corrected for a skew. This is done
to synchronize and match the placement of a particular workpiece into,
for example, the middle of a corresponding lug space as the workpiece
exits the downstream end of lug loading section 12. Thus as may be seen,
the acceleration or deceleration of the sequence of workpieces 14 being
translated downstream over the sequential array of pairs of belts 38, 40,
42, 44 and 46, are selectively motion controlled so as to place a
workpiece 14 entering onto the upstream end of the lugged outfeed chains
32 preferably into for example the middle of a corresponding lug space or
otherwise exiting off the downstream end of belts 46 just after a pair of
lugs 32a rotate to the vertical as chains 32 rotate endlessly around
sprockets 48.

[0031]In the illustrated embodiment, not intended to be limiting, lug
loading section 12 has six control zone belt pairs may be thought of as
six belt modules each approximately sixteen inches long in the downstream
direction for a total downstream length of eight feet. In one preferred
embodiment, the motors 50 which selectively individually drive each belt
in each belt module, may be servo motors having corresponding gear heads.

[0032]It is understood that sensors 52 such as seen in FIG. 3 and known in
the prior art, and as would be known to one skilled in the art, would be
provided to detect the position of individual boards and that the
information from the sensors is processed by a digital processor 54
cooperating with the sensors and that the digital processors also
cooperates with a programmable logic controller (PLC) 56 via network 58
which in turn cooperates with the motors for selectively driving the
belts 22, 24, 26, 28 and 30 in gapping section 10 and belts 36, 38, 40,
42, 44 and 46 in lug loading section 12.

[0033]In interpreting both the specification and the claims, all terms
should be interpreted in the broadest possible manner consistent with the
context. In particular, the terms "comprises" and "comprising" should be
interpreted as referring to elements, components, or steps in a
nonexclusive manner, indicating that the referenced elements, components,
or steps maybe present, or utilized, or combined with other elements,
components, or steps that are not expressly referenced.

[0034]As will be apparent to those skilled in the art in the light of the
foregoing disclosure, many alterations and modifications are possible in
the practice of this invention without departing from the spirit or scope
thereof. Accordingly, the scope of the invention is to be construed in
accordance with the substance defined by the following claims.